It is already well known to use a "carpenter's cramp" wherein there is provided a post or bar, a lower anvil or jaw outstanding from the post, and a sliding arm, the sliding arm terminating in a threaded nut at its outer end which is threadably engaged by a screw-threaded member having a ball at one end and a handle at the other, the ball supporting a moving jaw for universal movement. Universal movement is considered necessary because of the change of angle of the arm as the cramp is tightened on a workpiece. Upon aging, the clamping jaw tends to rotate with its screw threaded member, and workpiece clamping becomes difficult.
Thus in U.S. Pat. No. 153,133 (Van Wagoner) there was described and illustrated a clamp wherein a moving arm was tilted with respect to a fixed post, the moving arm terminating in a ball-jointed clamping jaw.
U.S. Pat. No. 237,431 (Colt) discloses a sliding arm which locks upon tilting with respect to a fixed post, and a ball-jointed clamp jaw.
U.S. Pat. No. 248,949 (Pope) similarly discloses a sliding arm which locks upon tilting, and a screw threaded clamp jaw with a rotatable clamping member on one end of the thread, which is otherwise exposed to damage.
U.S. Pat. Nos. 437,403 (Nacke & Brinkmann), and 674,278 (McNutt) also each disclose a ball-jointed clamp jaw.
This invention relates to an adjustment clamp which also has an arm which slides over a post, and has as its main object the provision of a clamping jaw which is guided to remain parallel to the fixed jaw, and to avoid rotation by means other than engagement with the workpiece. A secondary object of the invention is to provide an adjustment clamp wherein the threaded member is reasonably well protected from damage due to weld spatter, paint or other material.